I ran 13.84 @ 100.99 last year with the 3.70 gear in the car. The car has a wide ratio trans and at best pulls 2.0 60 foot times. But I do not shift into 4th until just before the finish line, and I buzz the traps at a leisurely 4200 or so. This year I have the chance to upgrade to a 4.56 for the car. Figuring on a top end speed of 103, that would put the rmps near 6500 at the traps. sound like over kill or reasonable ??? I wanted a 4.11 but the all I found were 4.56s.........
Gears are good, and a SB Chebbie's likes RPM's. Hell the ol' man spun his 302 to 10 grand with 5.13's in the back. Granted, it wasn't entirely stock...... :laugh: Wish he would have saved the 68 Z for me instead of totaling it. :shock:
You'll run 6250 at 105mph with 26 inch tall tires! The taller the tire the the less rpm. The question should be is, do you drive the car on the street often enough for the rpm to concern you? Jim :bglasses:
I do like to drive the car, but with a vette a gear change is a Saturday afternoon project.............. don't even have to disconnect the brake lines :Smarty: the tire diameter is 26.9 so the mph would be 109.6 at 6250. I should be so lucky :rant: Tooling around town at 45 will take 2700 rpms........ I guess my big concern is the wide ratio (2.52 first gear) with that big a gear, it's the mathematical equivolent of having a 5.23 rear gear with a close ratio (2.20 first gear): is my little 327 going to be able to pull it ??
First gear is going to go by pretty quick. Maybe calculate your rpm drop for the 1-2 and 2-3 shifts, see if the motor will stay in your power band. There's only one way to find out, Donny - wind 'er up!
1st gear shifting at 6200 43 mph 2nd gear drop to 4700 2nd gear shifting at 6200 58 mph 3rd gear drop to 4850 3rd gear shifting at 6200 74 mph 4th gear drop to 4200 ( the shift points reflect the hydraulic cam )
2.52 First?....Run it My '61 Vette with the 283 had a 2.88 first gear with a 4.56 rear. Did not have a problem with first being too quick. Wheel spin was under control. It went 13.60 @ 103 best. The 1-2 ratio spread was a little too much for the 283 so second was noticably sluggish after the shift. My next step was to be the correct 2.20 gear trans and a 4.88 rear. I think it would have been quicker. The Merc has a 4.56 also.
Donny: I run the original M20 wide ratio (2.56 1st gear) with a 4.56 rear in the Ramrod with G70 x 14 Polyglas. I love that low gear. The little bit you lose in RPM drop between gears is more than covered by the 60 foot time improvement. I thought for sure that the car would smoke the tires out of the hole and will if i just dump it all at once. But once you get the "feel" of the traction, soft release, soft down on the throttle with a so-so wrap on the seconcary flapper door (Qjet), and let it spin a little (to keep the R's up and avoid the bog, the tires pull very hard. I was pulling regular 1.95 60 footers last year and had a coupla 1.90's when everything was right and I let it go at 4000. Usually 2500. At 100 MPH, the car went through the traps at 5700 (small cam last year). At 104 a few years back, the car went through the traps at 6200.
If you haven't yet tried it, you may be able to "zero lash" the valves and wind it up like solid lifters. You back the rockers off till they clatter then tighten them down till the noise just stops. No extra preload on the lifters. No 1/4 turn, no 1/2 turn, just till the rattle stops. Should let the engine wind a little tighter. Best thing....? it's FREE HORSEPOWER :3gears:
I think it's a great idea!!! Throw in the gears..... slap on some cowboy boots, and have at 'er!! :Brow: I predict at least a 3 tenths quicker minimum! :3gears: Peter
It makes the cam look bigger, and will rev higher, no doubt, But................ Don't do this with stock lifters with the wire ring retainer. Running it at or near zero lash is hammering that little piece of wire and if the lifters pump up (and they all do) after it is weakened, they break. If you're lucky like mine, all it did was break a rocker and run on 7 until I got it home. Found all pieces of the wire retainer in the head. Just had to pull the intake, replace the lifter, and change the rocker. This was on a 65 442 with a non adjustable system. But if you're unlucky like Rob was, the little pieces of that wire retainer can go into the oiling system through the screen on the pickup and get into the oil pump. In his case, it locked the pump, broke the oil pump drive shaft, and ate up the lower end of a fresh engine. There's preload on a lifter for a reason. Nothing wrong with running .020 or maybe even .010, but you better check and reset often just in case. You'll love the launch with that big gear. We ran 14.0's with the original 3.91, changed to a 4.10 and dropped to 13.70's, then changed to the 4.56 and dropped into the 13.50's with a coupla 13.40 and even one 13.30 run. This was when the engine was first rebuilt (before all the cam disasters) and was the only changes made. Top end MPH didn't change that much between the 4.10 and the 4.56, just got there quicker.
I've seen that little guy at many cruise nights, but usually hiding his face. Nice hood! :TU: Priceless picture!
I have a video of a big time NMCA fastback Vette like this that went up on its left side, then right side, then hit the LH guard rail hard at Norwalk a few years back. Driver was OK, but car was a disaster. Something broke in his suspension and it made a right turn at about half track, then side to side bouncing. Showed the video to the driver afterwards and he said he wasn't scared until he saw that.
